<h4>Tool</h4><table border="0"><tr><td valign="top"><b>Name</b></td><td valign="top">TPI Based Landform Classification</td></tr><tr><td valign="top"><b>ID</b></td><td valign="top">19</td></tr><tr><td valign="top"><b>Author</b></td><td valign="top">O.Conrad (c) 2011</td></tr><tr><td valign="top"><b>Specification</b></td><td valign="top">grid</td></tr></table><hr><h4>Description</h4>Topographic Position Index (TPI) calculation as proposed by Guisan et al. (1999). This is literally the same as the difference to the mean calculation (residual analysis) proposed by Wilson & Gallant (2000).
The bandwidth parameter for distance weighting is given as percentage of the (outer) radius.
<hr><h4>References</h4><ul><li><b>Guisan, A., Weiss, S.B., Weiss, A.D. (1999):</b> GLM versus CCA spatial modeling of plant species distribution. Plant Ecology 143: 107-122.</li><li><b>Weiss, A.D. (2000):</b> Topographic Position and Landforms Analysis. <a target="_blank" href="http://www.jennessent.com/downloads/tpi-poster-tnc_18x22.pdf">poster</a>.</li><li><b>Wilson, J.P. & Gallant, J.C. (2000):</b> Terrain Analysis - Principles and Applications.</li></ul><hr><h4>Parameters</h4><table border="1" width="100%" valign="top" cellpadding="5" rules="all"><tr><th>Name</th><th>Type</th><th>Identifier</th><th>Description</th><th>Constraints</th></tr>
<tr><th colspan="5">Input</th></tr><tr><td>Elevation </td><td>Grid (input)</td><td>DEM</td><td></td><td></td></tr><tr><th colspan="5">Output</th></tr><tr><td>Landforms</td><td>Grid (output)</td><td>LANDFORMS</td><td></td><td></td></tr><tr><th colspan="5">Options</th></tr><tr><td>Small Scale</td><td>Value range</td><td>RADIUS_A</td><td>radius in map units</td><td></td></tr><tr><td>Large Scale</td><td>Value range</td><td>RADIUS_B</td><td>kernel radius in map units</td><td></td></tr><tr><td>Weighting Function</td><td>Choice</td><td>DW_WEIGHTING</td><td></td><td>Available Choices:
[0] no distance weighting
[1] inverse distance to a power
[2] exponential
[3] gaussian weighting
Default: 0</td></tr><tr><td>Inverse Distance Weighting Power</td><td>Floating point</td><td>DW_IDW_POWER</td><td></td><td>Minimum: 0.000000
Default: 1.000000</td></tr><tr><td>Inverse Distance Offset</td><td>Boolean</td><td>DW_IDW_OFFSET</td><td>Calculates weights for distance plus one, avoiding division by zero for zero distances</td><td>Default: 1</td></tr><tr><td>Gaussian and Exponential Weighting Bandwidth</td><td>Floating point</td><td>DW_BANDWIDTH</td><td></td><td>Minimum: 0.000000
Default: 75.000000</td></tr></table>